[libvirt] problem of escaped scancodes

Tue Aug 23 13:54:11 UTC 2011

On Tue, Aug 23, 2011 at 03:32:51PM +0800, Lai Jiangshan wrote:
> 
> Hi, Daniel P. Berrange,
> 
> Our user found that some keycode can not be handled well when
> they try to map other keycode to xt_kbd keycode, when xt_kbd keycode
> is an escaped scancode.
> 
> The xt_kbd keycode http://git.gnome.org/browse/gtk-vnc/plain/src/keymaps.csv
> are come from x86_keycodes[] of linux/drivers/char/keyboard.c.
> And x86_keycodes[] are:
> 
> static const unsigned short x86_keycodes[256] =
> 	{ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15,
> 	 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
> 	 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47,
> 	 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63,
> 	 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79,
> 	 80, 81, 82, 83, 84,118, 86, 87, 88,115,120,119,121,112,123, 92,
> 	284,285,309,  0,312, 91,327,328,329,331,333,335,336,337,338,339,
> 	367,288,302,304,350, 89,334,326,267,126,268,269,125,347,348,349,
> 	360,261,262,263,268,376,100,101,321,316,373,286,289,102,351,355,
> 	103,104,105,275,287,279,258,106,274,107,294,364,358,363,362,361,
> 	291,108,381,281,290,272,292,305,280, 99,112,257,306,359,113,114,
> 	264,117,271,374,379,265,266, 93, 94, 95, 85,259,375,260, 90,116,
> 	377,109,111,277,278,282,283,295,296,297,299,300,301,293,303,307,
> 	308,310,313,314,315,317,318,319,320,357,322,323,324,325,276,330,
> 	332,340,365,342,343,344,345,346,356,270,341,368,369,370,371,372 };
> 
> 
> There is no keycode in range [128, 256] in this table, which means
> all escaped scancode "e0 ??" are encoded as "0x100 | ??" in this table.
> Example, LeftCtrl is 0x1d, and RightCtrl is escaped: "e0 1d",
> RightCtrl is encoded as "0x100 | 0x1d"(=0x11d=285) in this table.
> The code also tell me the same information:
> 
> 		code = x86_keycodes[keycode];
> 		if (!code)
> 			return -1;
> 
> 		if (code & 0x100)
> 			put_queue(vc, 0xe0);
> 		put_queue(vc, (code & 0x7f) | up_flag);
> 
> 
> 
> But some other place, escaped scancode "e0 ??" are encoded as "0x80 | ??",
> this encoding is more commonly used, and qemu uses this encoding,
> RightCtrl is encoded as "0x80 | 0x1d"(=0x9d=157) in qemu:
> 
>     { 0x9d, "ctrl_r" },
> 
>         keycode = keycodes[i];
>         if (keycode & 0x80)
>             kbd_put_keycode(0xe0);
>         kbd_put_keycode(keycode & 0x7f);
> 
> 
> The problem:
> keymaps.csv uses the first encoding while qemu uses the second one, it
> causes "virsh send-key" command can't work when it sends escaped scancodes.

What this acutally means is that we have 2 different scancode sets,
each with their own different encoding for the extended scancodes.
We are simply using the wrong set when talking to QEMU.

> Example:
> When do "virsh send-key domain KEY_RIGHTCTRL", qemu will receive keycode=285
> which is not expected.
> 
> So I suggest to change keymaps.csv.
> Covert the old
> KEY_RIGHTCTRL,97,RightControl,0x3e,,,88,,285,228,VK_RCONTROL,0xa3,0x65,0x65
> to new
> KEY_RIGHTCTRL,97,RightControl,0x3e,,,88,,157,228,VK_RCONTROL,0xa3,0x65,0x65
> (ditto for other escaped scancodes)
> 
> Or just add the new line to keymaps.csv followed by the old line, and make
> 285 and 157 can work at the same time.

No, we just need to switch to use the correct scancode set.

The original keymap-gen.pl script in GTK-VNC has code for auto-generating
the RFB scancode set, from the data for the XT KBD scancode set. It is a
straighforward re-encoding for the extended keys:

    # RFB keycodes are XT kbd keycodes with a slightly
    # different encoding of 0xe0 scan codes. RFB uses
    # the high bit of the first byte, instead of the low
    # bit of the second byte.
    rfbkey = (xtkbdkey & 0x100) >> 1 | (ktkbdkey & 0x7f)

Regards,
Daniel
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